The present invention relates to the field of processors having means for detecting the presence of an invisible source and its position in the field of view of the system. The present invention is a system for visually imaging the invisible.
Infrared and ultraviolet are invisible to the naked eye. In many applications it is advantageous if not imperative to detect and locate the source of infrared or ultraviolet radiation. Some employments of such devices are numerous military applications wherein, such as, the heat of an enemy gun or rifle barrel need be detected and its position located before countermeasures can be efficiently injected. Domestic applications include identification of hot spots in a burned out forest so that measures can be taken to prevent rekindling of the fire, among many others. Heretofor, most infrared-to-visual conversions were accomplished electronically wherein the image presented to an observer was electronically generated; and nearly all such prior devices are heavy, bulky, complex and sensitive to shock, which reduces their portability and increases their cost.
One prior device of which the present invention is an improvement thereover employs matched reticles with pseudo-random patterns, that are spatially oriented and synchronously driven. A photodetector behind the first sensor radiation within the field of view and provides an output which is then amplified. The amplified output drives a glow modulator that illuminates the second reticle with visible light having an intensity proportional to the magnitude of the amplified electrical output inputted thereto. The pattern of the light transmitted by the second reticle corresponds to the reticle's pattern that is illuminated at the moment. The total of the transmissions per rotation consists of a set of illumination patterns of various intensities. Like the present invention, their sum identifies the position of the source in the field of view of the system with a visible bright spot within an illuminated field.
The present invention simplifies the prior art by employing an on-off illumination source which, when coupled with the rotating, patterned reticle, will provide a set of illuminated patterns of equal intensity. That is, the illuminated portions are not weighted by intensity, and therefor, need not be processed as such. The result is a gray field of 25% maximum illumination having bright spot(s) of 50% maximum illumination corresponding to the source(s) of infrared radiation within the field of the system.